The prior art endoscope referred to above is composed of certain basic elements, namely a control unit, a first flexible tube having a free end connected to the control unit and an optical transmission system in the first flexible tube connected to the control unit for viewing outside images. Circumscribing a portion of the first flexible tube is a guide tube (second flexible tube) that is used in combination with a device circumscribing the terminal end portion of the first flexible tube (near the free end of the first flexible tube) to incrementally help advance the combination of endoscope and guide tube along a narrow passageway, such as a human colon. The incremental advance is achieved by first advancing the first flexible tube (endoscope) a short distance into the passageway sought to be penetrated and beyond the end of the guide tube, then the guide tube is advanced a predetermined distance over the first flexible tube. This procedure is repeated over and over until the location within the cavity sought to be penetrated is reached.
It has been found that there exists a relationship between the flexibility of the guiding tube and the flexibility of the first flexible tube (endoscope) relative to the ease of use of such apparatus. When the flexibility of the guiding tube and the endoscope are essentially the same, there are certain instances where the advancement of the endoscope beyond the guiding tube and then the advancement of the guiding tube over the endoscope creates problems either to the operator or to the patient. In operation, when the endoscope (first flexible tube) is advanced, the guiding tube is held stationary. It has been found that it is easier to advance the endoscope through the guiding tube if the guiding tube is stiffer than the endoscope, and it is easier to advance the guiding tube over the endoscope if the guiding tube was more flexible than the endoscope. It was further realized that the change in flexibility of stiff to flexible and from flexible to stiff of the guiding tube should be under the control of the person using it. Thus, the operator of the improved endoscope of the instant invention has control over the flexibility of the guiding tube or the endoscope relative to when it will become more flexible and when it will become less flexible.
To fully appreciate the understanding of the instant invention, the invention disclosed by U.S. Pat. No. 4,577,621 should be consulted. The means disclosed and claimed in this patent for advancing the free end of an endoscope along a narrow passageway, are shown in FIGS. 2, 3, 4(a), 4(b), 5, 6(a), 6(b), 7(a), 7(b), 8a, and 8(b) of this patent. Such means per se form no part of the novelty of the present invention, but may form a part in the overall combination as herein disclosed and claimed. Any such means are believed to be adequately described in the specification of U.S. Pat. No. 4,577,621, and such disclosure is incorporated herein by express reference.